DESCRIPTION: Measles remains a significant public health concern, and the NIH has committed itself to the development of a better vaccine against measles and the exploration of the immunogenetics of vaccine responsiveness. The Specific Aims of this research application extend previous data of the investigators by examining the influence of two antigen-processing genes (TAP: Transporter associated with Antigen Processing and HLA-DM) upon variations in antibody levels following measles vaccination. Specific Aim 1) By drawing upon the original cohort of Rochester school children, this study will provide estimates of the association between antibody level following measles vaccine and specific alleles of TAP and DM alleles in human subjects. Specific Aim 2) This study will also estimate the association between antibody level following measles vaccine and homozygosity of specific TAP and DM alleles in human subjects. Specific Aim 3) Using class I and II HLA results from the investigators current study, they will estimate the association between the antibody level following measles vaccination and extended haplotypes of HLA including class I and II as well as TAP and DM. Hypotheses under study examine children with both extremes of measles antibody levels following vaccination: low and high antibody levels. Specific Aim 4) Studying the parents and siblings of the children with both extremes of antibody levels will permit examination of the genetic linkage between antibody levels following measles vaccination and TAP and DM loci within pedigrees. By focusing upon genes within the Major Histocompatibility Complex (MHC) responsible for antigen transport, processing, and presentation, these four aims will provide data that will help define genetic influences on measles antibody levels following vaccination. The public health relevance of this work may be significant since such information is likely to generalize to other live virus vaccines such as rubella, mumps, and varicella, and be instrumental in developing the next generation of measles vaccines.